Fine physicochemical, structural, rheological and gelling properties of tomato pectin under infrared peeling technique

To protect the pulp quality, the effect of infrared peeling on the physicochemical, structural, rheological, and gelling properties of tomato pectin was investigated using newly developed catalytic infrared peeling equipment and compared with manual, hot-water and lye peeling. Compared to manually peeled pectin, the results showed that hot-water peeling reduced the pectin yield by 13.19% but significantly increased the pectin's Z-average radius of gyration (R_g) and hydrodynamic radius (R_H). And the pectin gel had excessive hardness. Lye peeling reduced the pectin yield by 30.43%, the degree of esterification (DE) by 25.97%, R_H by 7.8 nm and R_g by 2.9 nm. And the pectin gel had the worst water-holding capacity and texture. The yield and DE of pectin (IPP) after infrared peeling only decreased by 3.88% and 0.9%. IPP exhibited moderate physicochemical, structural, rheological, and gelling properties, which was the closest to manually peeled pectin. IPP gel showed steady viscoelasticity and high water-holding capacity (96.71%). Conclusively, the infrared peeling technique can provide better pulp quality and is sustainable.